We compute activity coefficients of a solvating component that forms a bimolecular complex. In the first notebook, we show calculation of activity coefficients where only chemical interactions are considered. In the second notebook, we present calculations of activity coefficients where both chemical and physical interactions are taken into account. This problem was presented in the paper by H. G. Harris and J. M. Prausnitz, Thermodynamics of Solutions with Physical and Chemical Interactions, Solubility of Acetylene in Organic Solvents, I&EC Fundamentals, Vol 8, NO. 2, May 1969, pp 180-188. Computation of activity coefficients in solvated mixtures is also described in the excellent book by Prausnitz et al., Molecular Thermodynamics of Fluid Phase Equilibria, 3rd Edition, Prentice Hall, 1999.